The cloning and expression of the recombinant osteogenic proteins of the BMP-2 family has previously been described (J. M. Wozney, et al., Science 242:1528-1534 (1988); E. A. Wang, et al., Proc. Natl. Acad. Sci. USA 87:2220-2224 (1990), incorporated herein by reference). Osteogenic proteins of the BMP-2 family are a promising development in the bone and cartilage field. The BMP-2 family of proteins includes BMP-3, BMP-4, BMP-5, BMP-6 and BMP-7, and bone-inducing proteins and proteins which are encoded by DNA sequences which hybridize thereto under stringent conditions.
The BMP proteins include BMP-1, BMP-2, BMP-3, BMP-4, BMP-5, BMP-6 and BMP-7, disclosed for instance in United States Patents 5,108,922; 5,013,649; 5,116,738; 5,106,748; 5,187,076; and 5,141,905; BMP-8, disclosed in PCT publication WO91/18098; BMP-9, disclosed in PCT publication WO93/00432; and BMP-10, disclosed in co-pending patent application, serial number 08/061,695, filed on May 12, 1993, now abandoned. They may also include other proteins of the TGF-.beta. superfamily of proteins, such as activins. Examples of activin proteins which may be used in accordance with the methods of the present invention is described in co-pending patent application 08/061,464, filed on May 12, 1993, now abandoned. Examples of members of the TGF-.beta. superfamily of proteins which may be used in accordance with the present invention are Vi-1 and VL-1, which are described in copending patent application 08/164,103, filed on Dec. 7, 1993, now abandoned. The methods of the present invention are also useful with heterodimers of the above BMP proteins and TGF-.beta. proteins. Examples of preparation of such heterodimers are described in copending patent application Ser. No. 07/989,847, filed on Nov. 27, 1992. The disclosures of all of the above references are incorporated herein by reference.
These osteogenic proteins may be produced in cultured mammalian cell lines by transformation with an expression vector containing the respective cDNAs. The yield of expressed recombinant bone-inducing proteins can be increased in accordance with the present invention by addition of dextran sulfate to the cell culture medium.